Submission #2623158

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Source Code Expand

#include <bits/stdc++.h>
#include <unistd.h>
#define ll long long
#define inf 1000000007
#define inf16 0x3f3f3f3f
#define INF 1000000000000000007LL
#define VI vector<int>
#define VPII vector<pair<int, int> >
#define VLL vector<ll>
#define PII pair<int, int>
#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define endl '\n'
#define ALL(c) (c).begin(), (c).end()
using namespace std;

const int N = 1e5+7;

int n, ans;

int A[N];
int B[N];

PII mB[N]; //maksymalne B dla danego A
PII mA[N]; //maksymalne A dla danego B

map<PII, int> takie;

int32_t main()
{
	ios_base::sync_with_stdio(0);
	cin.tie(NULL);

	cin >> n;

	for(int i = 1; i <= n; ++i)
	{
		cin >> A[i] >> B[i];
		takie[{A[i], B[i]}] = i;
		mB[A[i]] = max(mB[A[i]], mp(B[i], i));
		mA[B[i]] = max(mA[B[i]], mp(A[i], i));
	}

	if(A[2]!=B[1] || A[1] || B[2])
	{
		cout << -1 << endl;
		return 0;
	}

	if(A[2]==1)
		++ans;

	for(int i = 3; i <= n; ++i)
	{
		if(takie.find({A[i]-1, B[i]-1})!=takie.end())
			++ans;
		else
		{
			if(mB[A[i]-1].st>B[i]-1 && mA[B[i]-1].st>A[i]-1)
				ans += 2;
			else
			{
				cout << -1 << endl;
				return 0;
			}
		}
	}

	cout << ans << endl;
}

Submission Info

Judge Result